1. Field of the Invention
The present invention relates to an information apparatus and its information network system for treating digital contents data such as picture and music.
2. Description of the Related Art
Recently, digitalization of picture and music has been promoted and many digital apparatuses have been introduced into homes. As for broadcasting systems, digitalization of ground wave broadcasting is making progress and broadcasting system will be shifted completely to digital television broadcasting with ground wave in 2011, for example, in Japan. Corresponding to the ground wave digital broadcasting, each of an electric machine company has started to sell various AV (Audio and Visual) digital apparatuses. These days, digital recording/playback apparatuses such as DVRs (Digital Video Recorders) have particularly attracted attention. A DVR can record an image to a digital recording medium (HDD, DVD-RAM, DVD-R, memory card, etc.) by digital-processing, thereby it is possible to save contents data of clear picture without degradation of picture quality over a long period.
Further, the DVR enables the contents data to be moved between the recording media. Since there is no degradation of picture data even if the contents data is moved or duplicated, distributors of original contents such as picture and music claim copyright protection for the contents data. In the meantime, the manufacturers have also been developing DVR equipments to correspond to the copyright protection.
When the contents data is recorded to the DVR, it is recorded in a format called MPEG (Moving Picture Experts Group) 2, which is one of video data compression methods. As one of the DVR functions, there is a function to move contents data to a memory card. The contents data that is moved to the memory card can be watched and heard by a portable terminal and the like. The contents data recorded in high picture quality has a large amount of information, so that it is impossible to move the contents data if the capacity of the memory card is small. In such a case, data is converted into MPEG4 format. By reducing the volume through converting the format of the contents data to MPEG4 format that has a much higher compression rate, it becomes possible to move the data to the memory card. However, the picture quality of the MPEG4 format is degraded in comparison to the contents data (original) of MPEG2 format. In case of data-movement different from data duplication, there is no contents data (as a target of data-movement) remained in the medium with the original data after the data movement since the original contents data is deleted along with the data movement. As a result, when a certain contents data is moved from the DVR to the memory card, and is again moved from the memory card to the DVR, the contents data in the DVR becomes deteriorated.
Therefore, it has been given some idea that the picture quality at original-level can be restored when the data is moved again to the DVR. FIG. 11 shows the schematic view of such DVR according to the prior art.
Original contents data CO is recorded to an internal recording medium 51. The contents data CO is moved to a memory card 30. For moving the data, volume is reduced by converting the data from MPEG2 format to MPEG4 format. At that time, the picture quality is deteriorated. The obtained contents data C4 in MPEG4 format is moved to the memory card 30. At the time of data movement, an encryption key generating device 52 is started to generate an encryption key KD, and the original contents data in MPEG2 format is encrypted by using the encryption key KD. The encrypted contents data C2 is saved in the internal recording medium 51 and at the same time the original contents data CO are deleted. Specifically, the original contents data CO is saved in a state where it cannot be accessed normally, which seems to be deleted on the appearance. With this, the encrypted contents data C2, which is the original-level data without degradation of picture quality, is saved in the internal recording medium 51. The encryption key KD used is saved in the memory card 30, and when there occurs a request of data movement to DVR 400 from the memory card 30, the encryption key KD is obtained from the memory card 30 to decrypt the encrypted contents data C2 saved using the encryption key KD. In this case, the encryption key KD in the memory card 30 is deleted. As mentioned above, it is possible to restore the picture quality at original-level even if data movement is again carried out to the DVR.
As a prior art relating to the present invention, as disclosed in Japanese Published Patent Literature (Japanese Patent Unexamined Publication 2004-5526), for example, there is a contents-utilizing system to settle user demands and copyright protection in a well-balanced manner by encrypting the contents key information by use of contents ID and a network key shared within the network.
As shown in FIG. 12, in the related art described above, it is possible to restore the picture quality at original level through moving the encryption key KD from the memory card 30 to the first DVR 400 under the state where the encrypted contents data C2 is saved in the first DVR 400. Thus, in the movement form where the data is moved from the memory card 30 to the first DVR 400 in which the encrypted contents data C2 is saved, it is possible to restore the picture quality at original level. However, in a movement form where the data is moved to a second DVR 500 in which the encrypted contents data C2 is not saved, the contents data C4 of MPEG4 format is simply moved. Therefore, it is not possible to restore the picture quality at original level.